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Brain tumors are clusters of cancerous cells growing in the brain. This article begins by describing cancers in general, and then moves onto an analysis of brain tumors in particular-- how they work, and what their effects are.
Humans never stop growing and developing, neither in their bodies nor in their brains. The adult body constantly forms new cells to replace old or damaged ones. Infants and children grow by forming new cells in addition to the cells they need to repair damage to their bodies. However, sometimes the machinery of growth and repair breaks down, and the body gives birth to clusters of unnecessary, abnormal cells, which act as parasites rather than healers and helpers. Known as cancers or tumors, these mutant cell clusters have the same genetic makeup as other cells in the body, but they remain frozen in a half-developed stage even as they multiply rapidly, fulfill no useful function in the body, and eventually suck up so many nutrients and take up so much space that they cause irreparable harm to vital organs. Although the mechanisms of cancer are roughly the same throughout the body, each organ where cancer develops seems to be associated with a different flavor of the disease and a host of unique symptoms. With cancer as with real estate, it’s about location, location, location. Cancers of vital organs such as the heart, liver or pancreas are far more dangerous than cancers in the more out-of-the way areas like the skin or the male prostate.
Once they have taken root, cancers evolve in one of two ways. They may remain in the regions of the body where they first appeared, and continue reproducing either slowly or not at all. These types of tumor are known as "benign” because the damage they do is limited and they are easily removed by surgery. When examined under a microscope, these benign tumors look only marginally different from their neighbor cells. Although they are not contributing to the general welfare of that complex community of cells known as the human body, they are not really hurting it either. They cause few symptoms and their presence rarely results in death.
The most dangerous types of cancer cells are known as "malignant," because they reproduce quickly, and spread from their original location to other organs by travelling through the bloodstream in a process known as "metastasis." Malignant tumors that have jumped from one organ to another are called "metastatic cancers." Malignant cancer cells have an unusual, even freakish appearance under the microscope; even though they grow very quickly, they bear little resemblance to any healthy cells either in their original location or, after they have metastasized, to cells in the other areas of the body to which they have spread.
There is a continuum between benign and malignant cells, from almost healthy to highly toxic. The stranger its appearance, the more likely a cancer cell is to reproduce quickly and metastasize. Metastatic cancers are the most dangerous of all cancers; they have the nastiest side effects and are the hardest to treat. Most are lethal. Hence, the most effective treatments catch a tumor early, before it has time either to metastasize or to grow so large that it interferes with the normal functioning of the organs nearby.
Brain tumors are usually benign, or "primary," in the narrow sense that most have originated in the brain or the spinal cord and will not metastasize. However, they can also be seen as malignant because of the risk they pose to vital life functions such as the heartbeat, breathing, appetite, or the capacity to reason embedded in the frontal lobe. Primary brain tumors occur in people of all ages, but tend to be more frequent in children and older adults. Meningiomas, or tumors of the delicate protective tissue around the brain and spinal cord known as meninges, represent 33.4% of all primary brain tumors, making them the most common primary brain tumor. Gliomas, tumors of the glue-like glial cells that support neurons and produce the myelin, the chemical insulation that allows neurons to send electric signals, are more dangerous than meningiomas. They represent 33% of all brain tumors and 80% of the brain tumors that become malignant.
Surgery may appear to be the most sensible treatment for early-stage benign brain tumors, because it involves a quick cut and removal of the cancerous growth before it can do much harm. And yet, surgery can also be dangerous when the tumor is located in a vital, delicate area such as the brain. It is built out of tissue so dense and specialized that the tiniest cut in the wrong place could have disastrous consequences for the patient -- memory loss, for example, or the loss of vital functions that can no longer be controlled by the brain.
The brain can also be the unwitting recipient of metastatic cancer cells. Cancers of the lung, breast, colon and skin -- the last of these is also called melanoma -- hitch a ride through the bloodstream to the brain, and hijack it on arrival, causing symptoms similar to those created by "primary" or localized brain tumors. They are much more common than any of the primary tumors, occurring four times as much, and like gliomas, they are difficult to treat and often lethal. |
